The effects of timolol maleate on intraocular pressure (IOP) and the severity of retinopathy induced by exposure to 80% oxygen were studied in newborn Wistar rats. One drop of timolol maleate (0.25%) instilled in each eye twice a day for the first ten days of life substantially reduced intraocular pressure without significantly modifying arterial pressure. Forty percent of the ratlings treated in this way failed to develop oxygen-induced retinopathy (OIR) after exposure to 80% oxygen for the first five days of life; in the other 60% OIR was less severe than that seen in an identically oxygenated group that did not receive timolol. The authors hypothesize that the pharmacologically induced reduction in IOP may have attenuated the effects of the high concentrations of oxygen on the immature retinal vessels by improving the ocular perfusion pressure. The possibility that timolol maleate also exerts a direct action on the caliber of these vessels cannot be excluded.
The present study reports on the immunohistochemical distribution of S-100 antigen in non-nervous cell types within the human eye at light microscopy. In the cornea the antigen was confined to endothelial cells covering its posterior surface; the lens exhibited immunoreactivity restricted to the epithelial cells located beneath the anterior capsule. In the iris and ciliary body, S-100 was detected in stromal cells and epithelial cells of the pigmented inner layer in the former and inner epithelial cells bounding the posterior chamber in the latter.
The authors describe a scoring system they have developed for evaluating damage produced in the retinal vascular network of the newborn rat by exposure to oxygen. India ink-injected retinal flat mounts are used. The scoring system provides for division of the retina into three concentric zones with the optic disk as a center point. Each retinal quadrant is then examined for the presence of the following lesions of progressive severity: vaso-obliteration of the capillary network, loss of the periarteriolar capillary-free zone, newly formed capillary tufts. When more than one type of lesion is present in a quadrant, only the most severe lesion is considered. The numerical score corresponding to that lesion is then multiplied by the factor corresponding to the concentric zone in which the lesion lies to give the quadrant score. The total retinal score is represented by the sum of the four quadrant scores. This type of system, if adopted by other investigators, can facilitate precise and systematic description of the results of different experimental protocols.
An experimental study was conducted to verify the effects of prolonged normobaric and hyperbaric oxygen supplementation on retinal vessels in newborn animals. Nine litters of newborn Wistar rats were used in the following way. Two litters were used as controls. Two other litters received normobaric oxygen supplementation (FiO2 80%) for five days after birth. These rats were then removed and kept for five more days in room air. Retinopathy with marked peripheral retinal neovascularization was seen in these litters. Three other litters were exposed to the same treatment for ten days after birth, removed from oxygen, and kept for 15 more days in room air. Severe retinopathy with extraretinal proliferation and, in some cases, retinal detachment developed in these animals. Two other litters received hyperbaric (1.80 atm) oxygen supplementation (FiO2 80%) for ten days after birth and were then kept for 15 days in normobaric room air. These animals showed no evidence of peripheral retinopathy. It is possible that moderate hyperbarism exerts, in the newborn rat, a protective action against the toxic effects of oxygen supplementation on immature retinal vessels.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.